Construction of the cooling zone of tunnel kilns, and especially though not essentially to such kilns for firing ceramic goods



Sept. 24, 1963 I G cREMER ETAL 3,104,442

CONSTRUCTION OF THE COOLING ZONE OF TUNNEL KILNS, AND

ESPECIALLY THOUGH NOT ESSENTIALLY TO SUCH KILNS FOR FIRING CERAMIC GOODS Filed OC. ll, 1960 4 Sheets-Sheet l dan( C42/mm.. @i Mm l? @Mx/2m Sept. 24, 1963 G. CREMER ETAL 3,104,442

CONSTRUCTION OF THE COOLING ZONE OF TUNNEL KILNS, AND

ESPECIALLY THOUGH NOT ESSENTIALLY TO SUCH KILNS FOR FIRING CERAMIC GOODS Filed oct( 11, 19Go 4 sheets-sheet z /7/ m--In-nl/ e a-iyz e /NVEN'ORS EMM y @L f2@ Sepf- 24, l963 G. CREMER ETAL 3,104,442

CONSTRUCTION OF THE COOLING ZONE OF TUNNEL KILNS, AND ESPECIALLY THOUGH NOT ESSENTIALLY TO SUCH KILNS FOR FIRING CERAMIC Goons Filed oct. 11, 1960 4 sheets-sheet s 64M? WM l @ma Sept. 24, 1963 G. cREMER ETAL 3,104,442

CONSTRUCTION OE THE COOLING ZONE 0E TUNNEL KILNS, AND

ESPECIALLY THOUGH NOT EssENTIALLy To SUCH KILNs FOR FIRING CERAMIC Goons Filed Oct. l1, 1960 4 Sheets-Sheet 4 4&6/ (7m. Af @2m United States Patent Oli ice 3,164,442 CONSTRUCTIN l? THE CGNQ ZNE 0F TUNNEL KELNS, ANB ESFECALLY THQUGH N675 ESSEN'iil-LLLY 'I0 SUCH KELNS FOR Figi-{Ni} Chliltil GBS Gottfried Qreiner, 6 Stey'rerweg, Coiogne-lnnlxersdori, and Heinz Behrens, 2@ Hauptstrasse, Schwarzenieid, Germany Filed Get. il, 196i), Ser. isle. @,864 Claims priority, application Germany Noi'. i2, i959 iti Claims. (El. -l42) rlhe invention relates to the construction of the cooling zone of tunnel kilns, and especially though not essenltially to such kilns for iiring ceramic and similar products.

In a known construction of the cooling zone of a tunnel kiln, cooling of the fired goods takes place simultaneously by radiation and convection to heat exchangers arranged in the kiln channel and ,traversed by a gaseous or liquid cooling medium. These heat exchangers are preferably arranged in chambers formed by ribs extending from the kiln arch transversely to the kiln channel and are adapted to be screened to a certain extent from the interior of the kiln channel for the purpose of regulating the cooling process.

This adjustable screening of the heat exchangers is accomplished in the known construction or" cooling zones by pairs of plateilike dampers of reproof material arranged below or ahead of the heat exchangers and lying in the kiln arch and/ orV the side walls of the kiln channel, and `supported by the ribs `forming the chambers or by lateral extensions thereof for movement towards and away from each other. 'llhese pairs of plate-like dampers leave a slit of variabile width between their opposing edges, through which the kiln atmosphere comes into direct contact with the heat exchangers and through which the cooling depending on radiation also takes place.

lIn this manner, however, only a comparatively rough adjustment of the cooling curve is possible. This is particularly disadvantageous where the mass of goods being tired (and so its heat capacity) varies appreciably in the longitudinal direction of the train of tiring bogies. This is, for example, particularly the case in the tiring of earthenware pipes of different diameters, where the gravinietric variations or" the fired masses to be cooled and the corresponding variation in quantity of heat to be dissipated can be as high as in the ratio 1.2, which has to be controlled by adjustment of the openings or the degree of screening of the cooling devices.

Another important ditiiculty, present not only in such extreme cases but also in norma-l ones, which arises from the lire adjustment of the effect of the heat exchangers required for satisfactory cooling of delicate ceramic goods is because the region within which direct connec'- tion takes place between the Iheat exchangers arranged in the kiln arch and the interior of the kiln channel always lies at the center of the arch. The slit formed between the inside edges of the dampers when suitably adjusted lthus has a chimney-like draught effect on the kiln atmosphere which results in unfavourable current conditions. Admittedly this may be tolerated in those temperature ranges in which rapid cooling is not dangerous and local differences therefore do not play such a decisive part; but this is not so in temperature ranges in which the goods being fired are particularly sensitive, as, for example, temperatures in the vicinity of the quartz conversion point (575 C.).

A further disadvantage of the known adjustable screening of the heat exchangers from the interior of the channel resides in the fact that the masses of the dampers (consisting of ceramic material) become so great vas the width of the kiln channel increases, that their free move- -jected.

3,104,442 Patented Sept. 24, 1963 ment through small distances, as is required particularly for automatic control is no longer possible. This disadvantage is particularly serious -because there is a desire to increase the width of tunnel kilns used in the ceramic industry as far as possible with a view to increasing their output; at present tunnel kilns .are already being used with a working width of the tunnel channel of 13 t'eet or more.

An object of thepresent invention is to overcome the aforesaid disadvantages and limitations and to provide iinely controllable and more or less far reaching screening of the heat exchangers from the kiln channel, in dependence on the variations in ,the :amount of heat lto be extracted from the goods to be cooled, either manually or, in particular, by automatic control of the operation of the screening device.

According to one aspect of lthe invention, this is achieved by subdividing the openings of variable size by which the kiln atmosphere gains access to the heat eX- changers in the transverse chambers into a plurality of such openings which are arranged, in the transverse direction of the kiln channel, in equidistant succession, spaced by bridges of appropriate width and provided with suitably constructed screening devices slidably arranged in the plane delined by the upper surfaces of the bridges.

Through these openings, which are preferably disposed in lateral regions of the kiln channel, a communication controllable by the position of the dempers is provided between the interior of the kiln channel and tlhe heart exchangers arranged above it at locations which are evenly distributed over thevwidth lof the kiln channel, thus eliminating the intensive chimney effect of a single opening provided at the centre of the kiln channel.

The arrangement and construction of these openings and of the dampers are preferably matched to the various conditions ruling in the various regions of the cooling zone.

In the region at the beginning of the cooling zone Where only rough control is required, subdivision into only two openings usually suffices. The middle region of the arch is screened from the heat exchangers by a single, xed, comparatively wide bridge, the openings being formed on either side thereof, and each being closable to a greater or lesser extent by an inwardly or outwardly movable damper of appreciably smaller weight.

The width of the openings and thus the size of the dampers is preferably substantially equal to the thickness of the side walls of the kiln channel, so that the dampers lie wholly within guide slits in the walls when in their fully retracted position, without protruding laterally fromY the kiln contour.

In theV zone of the kiln channel in which the goods tbeing tired traverse the dangerous range of temperatures, the openings are preferably further sub-divided, a plurality of damper members for the controllable closing of the openings being rigidly Vcoupled `by spacers of suitable construction, so that all the dampers can be moved simultaneously in one direction or the other byl operating rods which are preferably provided on each side. This may be done from one side of the kiln channel. l

In the case of a kiln channel of comparatively great Width the dampermernbers are conveniently'pulled to and fro alternately from one side of the channel to the other.

The damper members too may be diilerently constructed for successive zones, according to the rdiiierent temperature and insulation conditions to which they are vsub- In the hotter zones they preferably consist of lireproof ceramic material, preferably of light weight, suchV as one of the' known light weight refractories and, in Vthe zones of the lower temperature, ot `suitably temperature resistant sheet metal.

In the adjacent low temperature zones one-piece sheet metal dampers are preferably used which extend over the entire width of the kiln channel and which, in their basic construction, consist of a simple metal strip having rectangular openings suitably spaced apart by bridges. With a View to increasing the insulating elect of such a metal strip against the kiln atmosphere, the transverse bridges may, if desired, fbe covered with suitable insulating material which may be accommodated in grooves formed by sheet metal U-sections mounted on the dampers and simultaneously acting as stiiners therefor.

Where an improvement in the insulating effect is required smaller than that obtainable from covering the sheet metal damper with ceramic insulating material it may sulice to orin the dampers out of two or more relatively spaced layers of sheet metal.

The ceramic or sheet metal dampers are supported, in known manner, 'by mutually opposing lugs on the vertical ribs which separate the successive cooling zones in the longitudinal direction of the kiln.

l According to a further feature of the invention, the position of the dampers is controlled automatically, this `being by means of temperature sensing devices arranged in successive regions in the direction of advance of the Yfiring bogies and adjusted to a predetermined temperature, whereby control impulses are generated upon departure from this predetermined temperature, to cause movement of these screening means 4in an opening or closing direction. Thereby the temperature gradients in the successive sub-Zones which are individually regulated by the sensing devices, can be made greater in the regions of higher temperature and successively smaller in the regions of lower temperature; that is the temperature conditions are only roughly controlled in the first regions, but linely in the subsequent ones, the control being all the easier in the latter regions because very light and correspondingly easily movable screening devices are used therein.

' The temperature sensing devices in the various regions can also simultaneously control the passage of the cooling medium through the heat exchanger in a manner known per se.

The application of the basic concept of the invention to heat exchangers arranged in the side walls of the kiln channel requires no special explanation.

The above and other features of the invention will be 'apparent from the following description of constructional examples thereof, with reference to the accompanying drawings, in which:

' FIG. 1 is a vertical section through the top portion of a tunnel kiln with the known construction of adjustable screening of the heat exchanger,

FIG. 2 is a horizontal section on line A-B in FIG. 1 showing above the open and below the closed position of the dampers and FIG. 3 is a section on line C-D of FIG. 2,

1FIGS. 4 to 6 show one arrangement of screening devices according to the invention, the views corresponding to those of FIGS. 1 to 3,

FIGS. 7 to 9 show corresponding views of a second 'walls a', a covered by an internalV insulating layer b',

b and a cover c.

A train of ring bogies, of which only the charge d on one bogie is shown, passes through the free kiln channel. j

yFrom the cover c extend vertical ribs e spaced at intervals in the longitudinal direction of the kiln channel. These ribs are of inverted T-section and have lateral flanges It', h, heat exchangers f lie in the chamber-like spaces formed between the ribs e and are connected to outwardly extending feed and discharge conduits g for the cooling medium. l

Damper members i', i" rest on the lateral llanges t, h of the ribs e and comprise rectangular plates of cerramic material; they are slidable in the transverse direction of the kiln channel by means of rods k', k" provided with handles and extending through openings in the side y walis a', a" ot the kiln channels.

In the position according to the top portion of FIG. 2 the dempers completely close the openings formed between the mutually opposing lateral llanges'h of adjacent ibs e, and in the position shown in the bottom portion of FIG. 2 they leave open a central opening l which is symmetrical about the longitudinal axis of the kiln channel. Through this opening the kiln atmosphere gains access to the disposed.

FIGS. 4 to 6 show the first embodiment of the invention, namely one particularly suitable for the starting` region of the cooling zone in which the temperaturesfare still appreeiably above the quartz conversion point and only rough temperature control is required.

In this embodiment, the opening bet-Ween the supporting means or mutually opposed flanges h', h" of two successive vertical dividing means Ior ribs e is bridged in the central region by a fixed 4bridge m lying on the llanges h', h. material and which compared with tho-se of FIGS. 1 to` 3 are of considerably reduced width, are supported on the exch-angers over a controllable range via the openings 'Y formed on either side of the central bridge m.

In the construction according to FIGS. 7 to 9, an even further sub-division takes place as compared with that of FIGS. 4 to 6, namely into three openings o', o, 0" as shown. In this case the openings are formed by Itwo ytransverse bridgesp, p", which connect the mutually Vopposed llanges h', h. In this case four damper mem.- `bers q', q", q", qm' of somewhat greater width `than the openings o are used. These are connected to eachother, by pairs of rods r', r which also constitute spacers, at 'distances corresponding to the width of the openings o. The damper members are `arranged to slide in one or 4other direction so as to close the openings either entirely or partially or to leave them fully open. The dempers 'are moved by means of the actuating rods k', k" arrangedY on either side thereof. n

In the extreme left hand position, the second damper member q closes the opening o', the following one q" closes the opening o and the following oneq'f closes f the opening 0"', while the damper member q is out of action. In the extreme right y.hand position the sequence is reversed and the damper member 11" is out of action.

FIG. 8 shows two possible'positions of `the damper memj bers and of the controlla-ble adjustments -to the openingsV o' to o FIGS. 10 and 1l show -a damper which is particularly Vsuitable for the zones of low temperature. It-comprises `a rectangular sheet metal plate t, provided with openings s', s", s" and with actuating handles k', k" attached to the plate. FIGS. 12 and 13 show corresponding views of a different construction of such `a sheet metaldamper, Y

in which U-shaped sheet metal troughs are welded tothe ytransverse bridges separating the openings s of a like base spaces in which the |heatrexohangers .f are Darnpers n', n", which `also consist of ceramic Y 5 plate t, the troughs being filled with insulating material v.

The possible automatic .control `of the damper arrangement shown in :accordance with the temperature .co-nditions, by means of a temperature sensing device associated with each damper, is not shown in the drawings.

Obviously the invention is not confined to the constructions hereinbefore described in detail `and illustrated in the drawings; numerous modifications thereof are possible without departing from its basic concept.

We claim:

1. A tunnel kiln having ra cooling zone, a plurality of ribs in spaced longitudinal relation along said zone, said ribs providing `a plurality of chambers, a heat exchanger in each of said chambers, at least one bridge member extending between the ribs defining each charnber to provide openings on each side of said bridge member in communication with .the interior of said kiln and dampers for each of said openings movable to controllably screen said heat exchanger from the interior of said kiln.

2. A tunnel kiln comprising side walls, and an arch defining a cooling zone, transverse ribs spaced along the length of said zone and depending from said arch, said ribs defining a plurality of chambers, a heat exchanger in each of said chambers, a wide bridge member extending between each pair of ribs along the centre line or said -arch and defining with said side walls an opening on each side of said bridge .connecting said chamber with the in- Iterior of said kiln, and dampers slidable 'across each of Said .openings to `a controllable extent to screen said exchanger from the interior of -said kiln.

v3. A tunnel kiln comprising side walls, and an arch defining a cooling zone, transverse ribs spaced along the length of said zone and depending from said arch, said lribs defining a plurality of chambers and having lower fianges extending horizontally, a heat exchanger in each of said chambers, a wide bridge member extending between each pair of ribs along the center line of said arch and defining with said side walls an `opening on each side of said bridge connecting said chamber with the interior of said kiln and dampers supported on the horizontal flanges of said .ribs and slidable across each of said openings to a controllable extent to screen said exchanger from the interior of said kiln, said bridge lying above the plane of said horizontal ilanges with its side edges constituting stops limiting the sliding movement of the dampers.

4. A tunnel kiln comprising side Walls, and an farch defining a cooling zone, transverse ribs spaced along the length of said zone and depending `from said anch, said ribs defining a plurality of chambers, a heat exch-anger in each of said chambers, a plurality of bridge members extending parallel to one another between each pair of ribs and defining la plurality of openings connecting said chamber with the interior of said kiln, and dampers slidable .across each of said openings to .a controllable extent to screen said exchanger from the interior of said kiln.

5. A tunnel kiln comprising side walls, and an vanch defining a cooling zone, transverse ribs spaced `along the length of said zone .and depending yfrom said arch, said ribs defining a plurality of chambers, fa heat exchanger in each of said chambers, a plurality of bridge members extending parallel to yone another between each pair of -ribs 'and defining a plurality of openings connecting said chamber with the interior of said kiln, a plurality 'of dampers greater by one than .the number of said openings rand each oit-slightly greater width than the associated opening, rigid spacers connecting said dampers and means for moving said dampers simultaneously in a plane defined by the upper surfaces of said bridges.

6. A tunnel kiln as defined in claim 5 wherein said dampers are formed by a rectangular sheet metal plate having a plurality of openings therein.

7. A tunnel kiln as defined in claim 5 wherein said dampers are formed by a rectangular sheet metal plate having .a plurality of openings therein, channel members affixed to the pla-te between the openings land heat insulating material within said channel members.

8. A tunnel kiln comprising side walls, and an arch defining .a cooling zone, trans-verse ribs spaced along the length `of said Zone :and depending Ifrom said arch, said nibs defining a plurality of chambers, a heat exchanger in each of said chambers, a plurality of bridgemembers extending `parallel to one yanother between each pair of ribs and defining a plurality .of openings connecting said chamber with the interior of said kiln, .a plurality of dampers greater by one than the number of said openings rand each of slightly greater Width than the associated opening, rigid spacers connecting said dempers `and means for moving said dampers simultaneously in a plane defined bythe upper surface of said bridges.

9. A tunnel kiln having a cooling zone a plurality of dividing means defining chambers :adjacent the cooling zone, at least one bridge lmember extending between `adjacent dividing mem'bers defining each chamber yto provide openings on each side of said bridge member, each of said cham-bers communicating with the interior of the kiln through at least two openings, a heat exchanger in each of said chambers, means for passing cooling fluid through said exchangers, supporting means carried by said dividing means, and obturating means for each of said openings supported by said supporting means, said obturating means con-trollably 'adjustable to screen said heat exchanger frorn the interior of said kiln.

10. A tunnel kiln as defined in claim 9 including temperature sensing devices within the kiln tunnel, each device being associated with said obturating means, and means controlled by said temperature sensing devices to move said obturating means `across said openings.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A TUNNEL KILN HAVING A COOLING ZONE, A PLURALITY OF RIBS IN SPACED LONGITUDINAL RELATION ALONG SAID ZONE, SAID RIBS PROVIDING A PLURALITY OF CHAMBERS, A HEAT EXCHANGER IN EACH OF SAID CHAMBERS, AT LEAST ONE BRIDGE MEMBER EXTENDING BETWEEN THE RIBS DEFINING EACH CHAMBER TO PROVIDE OPENINGS ON EACH SIDE OF SAID BRIDGE MEMBER IN COMMUNICATION WITH THE INTERIOR OF SAID KILN AND DAMPERS FOR EACH OF SAID OPENINGS MOVABLE TO CONTROLLABLY SCREEN SAID HEAT EXCHANGER FROM THE INTERIOR OF SAID KILN. 